Preparation of hydrolyzable titanium sulfate solutions



Patented Mar. 17, 1953 PREPARATION OF HYDROLYZABLE TITA- NIUM SULFATE SOLUTIONS Robert VJ. McKinney, Wilmington, DeL, assignor to E. I. du Pont de Nemours and Company, Wilmington, DeL, a corporation of Delaware No Drawing. Application March 24, 1951, Serial No. 217,409

9 Claims.

This invention relates to the solubilization of titaniferous materials and particularly to the preparation of soluble titanium salts from the titanium containing raw materials available to the titanium pigment industries.

The most widely used process for the manufacture of titanium dioxide pigments comprises the preparation of titanium sulfate solutions by reaction of strong sulfuric acid with titanium ores and specifically with the iron containing titanium ore known as ilmenite. Ilmenite appears at various places on the earths surface and mining operations are conducted in India, Norway, Florida, New York State, Virginia and Canada with minor supplies forthcoming from other points such as Brazil and Australia. The titanium content of the various ore bodies varies and the same is true of the iron content. In addition, there is a variation in the percentage of iron that is present as ferric oxide. In general, the ores which are highest in titanium i. e. ores of the arizonite type are also highest in ferric oxide. For instance, the 52% titanium oxide ores of India are found to contain about one-third of the iron content as ferric oxide while the 60% ores of India contain two-thirds of the iron content as ferric oxide. The commercially available ilmenite fraction from the Trail Ridge (Florida) deposits analyze around 65% T102 with 7580% of the iron in the ferric state. These arizonite ores of high ferric iron content present unique problems in the titanium. pigment industries due to the decreased reactivity with sulfuric acid and the correspondingly lowered heat of reaction. It has been proposed to treat the ilmenite prior to its use in the pigment industry by reduction of the iron to the ferrous state so as to obtain greater reactivity with sulfuric acid. This requires an additional operation comprising a furnacing operation which is not completely satisfactory due to the fact that during the heating operation some of the titanium content is rendered more refractory and becomes unavailable in the surfation operation. When the high ferric iron ore is used without the preliminary treatment, a large amount of scrap iron is required to reduce the ferric iron content of the solution prior to its use in the preparation of titanium pigment. Such solutions are then too high in iron to be used in the hydrolytic operations of the titanium pigment industry and, ac cordingly, must be cooled to separate iron therefrom as ferrous sulfate crystals. Sulphuric acid at an added cost must be. added, preferably during the attack, equivalent to the metallic iron neces- 2 sary to reduce the ferric iron present in the ilmenite. This operation is customarily practiced in spite of the cost resulting therefrom.

A most recent development in the titanium industries is the availability of the enormous titanium deposits of eastern Canada and combining the separation of titanium therefrom with the production of metallic iron. These ores of Canada run about 35% titanium oxide with the remainder largely being iron oxide. These ores are to be smelted in an electric furnace in admixture with carbon to produce molten iron and a high titanium slag. The latter will contain titanium oxide, analyzing from about to TiOz With the remainder being primarily iron, calcium, magnesium, aluminum and silicon, which are largely contributed by the ore or by the reducing agent used in the furnacing operation. This slag is reactive to sulfuric acid and sulfate solutions of titanium may be prepared by an operation similar to the preparation of titanium sulfate solutions from ilmenite ores. In either case, the titaniferous material is ground to about or through 325 mesh screen and the reaction carried out by methods well understood in the titanium pigment industries. These slag materials contain a minor amount of ferrous oxide and no ferric oxide. In addition, there is a considerable portion of the titanium oxide in a reduced state and the attack mass gives a product which upon dissolving may contain considerable trivalent titanium. During the sulfation operation the reduced TiO2 content of the slag acts as a reducing agent on the strong sulphuric acid and part of the acid is lost as a lower oxide or as a hydrogen sulphide. As a result there is not only a loss of sulphuric acid but a fume nuisance. The resulting solution, if it contains appreciable reduced TiOz, is unsatisfactory for the hydrolysis since the trivalent titanium content of the liquor must be oxidized to be effectively hydrolyzed. A further disadvantage of the titaniferous type slag is the relatively high content of aluminum and magnesiumtypical slags. These impurities are substantially dissolved in the sulfation process and present in the acid recovered from the filtration of the hydrolyzed titanium dioxides. The presence of these impurities, in the amounts present in typical slagshas been found to complicate, in some cases to prohibit, the concentration of the acid for other commercial use.

As explained above, it is possible to use either type of titaniferous material in the preparation of titanium sulfate solutions in the pigment industry. Each of these raw materials presents certain disadvantages and necessitates changes in the plant operations when one is substituted for the other and I have conducted investigations into the matter of minimizing the problems which occur in changing the raw material being used in a specific plant for the manufacture of titanium pigment. Accordingly, I have discovered a novel method for preparing titanium sulfate solution which avoids the disadvantages enumerated above and simplifies processing operations. Such are the objects of my invention which will be discussed hereinbelow in considerable detail.

My invention broadly comprises the preparation of titanium sulfate solutions suitable for the recovery of pigmentary titanium dioxide therefrom by well known hydrolysis methods by reacting a mixture of a titaniferous ore and a titaniferous slag product with strong sulfuric acid thereby producing a solid mass containing soluble titanium sulfate which is then dissolved in an aqueous solvent to obtain the titanium sulfate solution.

A specific embodiment of my invention comprises admixing a finely-ground titaniferous ore such as is obtained from the Trail Ridge deposit of Florida and analyzing about 65% T102 and 21% iron with a finely-ground slag material such as results from the smelting of Canadian titanto 100% slag. The ilmenite was a Florida product analyzing 64.9% TlO2, 4.7% ferrous iron and 16.5% ferric iron and may be properly called an ore of the arizonite type. The slag was a Canadian product analyzing 73.7 T102, '7 .9 ferrous iron, 0.6% calcium oxide, 5.3% magnesium oxide, 4.8% aluminum oxide and 3.9 silica. The slag showed a residue of 3% on a 325 mesh screen while the ilmenite was slightly less finely-ground and showed a 5% residue on the same screen. The sulfuric acid attack was carried out using 155 lbs. of acid, of 93% strength, per 100 lbs. of ore.

The reaction between the sulfuric acid and the titaniferous raw material was carried out by mixing the ore with the acid at a temperature of about 115 C. A vigorous reaction took place and the reaction subsided within -40 minutes in each instance. The reaction product was allowed to age for 90 minutes after which it was dissolved in dilute sulfuric acid at 65 C. The T102 conversions were determined by the customary analytical methods and the results showed satisfactory conversion values for all attacks. The dissolving was carried out in the absence of metallic iron or other reducing agent and the values given in the tabulated data for the amount of iron needed to reduce the solution are the results of analytical determination and proper calculation. Pertinent data of each of these sulfuric acid attacks are given in Table I.

Table I Grams Ilmenite 100 60 50 46 44 34 0 Grams Sla 0 50 54 56 66 100 Percent TiOg Conversion. 92. 8 91. 8 90. 8 90. 9 92. 1 91.3 88. 7 Percent TiOz in Mud..- 61. 4 53. 2 50. 0 49. 9 45. l 48. 2 45. 2 gms./mud/l00 gmS. Sol. TiOg 12.6 16.9 20.3 20.0 19.1 19.8 28.2 ms. H 804 lost/100 gins. ore 0. 16 0.35 0.34 0.33 0.63 1. 42 11.52 gins. Fe needed/100 gms. ore 11.3 2.9 2. l 2. 1 1. 4 1.0 0. 9 Fe/TiOz in reduced Sol 554 306 273 259 267 229 110 iferous ore from the Allard Lage region of Canada using about equal parts of each of these titaniferous products and sulfating the said admixture with sulfuric acid having a strength of about 90% H2804 in a manner well understood and practiced in the titanium pigment industries. Such sulfation operations are described in U. S. Patent 1,889,027 and in subsequent publications. The sulfation product is a dry mass which may be dissolved in water or other aqueous solvent to give a titanium sulfate solution having dissolved therein the major portion of the iron which was present in the titaniferous materials used. In addition, it will contain the sulfates of other metal oxides which were present with the titaniferous materials. The sulfate solution resulting from the attack and dissolution of the complex titanium raw materials has a chemical composition that permits one to hydrolyze by well known thermal methods without changing the relationship between the main ingredients, namely, titanium, iron and acid. There is no need for removal of ferrous sulfate by refrigeration methods as practiced in the prior art and, likewise, the use of metallic iron as a reducing agent may be dispensed with by my invention. The dissolved product without substantial change but after physical removal of any suspended matter may be submitted to the hydrolytic methods practised in the pigment industry.

My invention is illustrated by a series of experiments which I have conducted and which will serve as examples. A series of six sulfation operations were carried out in which the ratio of ilmenite to slag was varied from 100% ilmenite It is easily observed from the above data that the most attractive results are obtained by the use of blends of slag and ilmenite. For example, there is avoidance of substantial fume losses which occur when using slag alone. However, the major advantage in using the complex raw material is the simplicity of the succeeding operations in the manufacture of titanium pigment. It is to be noted from the data shown above that reducing iron can be avoided completely or to a large ex-.

tent by using the combination of slag and ilmenite. This shortens the processing time in the plant and there is a corresponding increase in tonnage for a given size installation. A point of still greater significance from an operation standpoint is the data presented in the last line of Table I showing that when one uses about 65% to about 35% of ilmenite (i. e. 35-65% slag) one obtains a Fe/TlOz ratio of from about .35 to about .22 in the final solution. Such a range in ratios has been found quite satisfactory in the sulfate process for the production of titanium pigment and specifically in hydrolysis methods such as outlined in U. S. Patents 2,511,218, 2,479,637 and Reissues 18.590 and 18,854. In fact, solutions having an iron-TiOz ratio greater than about .35 require the removal of iron therefrom by a cooling operation and it follows that the solutions produced by my invention do not require the costly treatment which has been required of ilmenite solutions in the past. Another advantage results from the fact that the recovered acid from the hydrolysis of solutions derived from blends of ilmenite and slag can be concentrated in the usual acid concentrating: equipment for: commercial My invention permits:v less; costly plant; in;- stallation. for a given tonnage, due to the simplicity of. the operation. and the; only additional step required. is the blending. of; the. slag with the. ilmenite and this. may readily beaccomzplished by feeding the two materials. to; a, grinding. system in; the: proper; proportions. There is some advantage in cogrinding the two, products so as to be sure of intimate. association. of the two ingredients, and the. improved results which are. obtained by intimate mixing. However, this cogrinding is not essential and one may elect to separately grind. and depend, on mixing the ground material either before orafter suspension inv the sulfuric acid, reagent. The extent of, ore grinding is not; critical. in, the opera.- tion but. it is advisable to; grind. to. the point where around 90%. orv morespassthrough a, 325 mesh screen.

7 The titaniferous materials suitable for use in my improved solubilization. process may vary widely in composition and. the operation. as, outlined above is applicable to the commercially available arizonite type titanium ores and slag products. Furthermore, it is believed that the process will be quite satisfactory for anyvariation in composition of slag materials which may result from furnacing operations of titaniferous iron ores analyzing from about 2.0 to. 40%.- T102. Thev slag resulting from the ore body of eastern Quebec may be enriched to the 60.-80% TiOz range as compared to approximately 35 in the original ore. During the furnaci-ng operation the iron in the slag fraction is. correspondingly reduced and may reach. as; low add-10%. .t is of particular significance that in this f-urnaoing step a substantial proportion of the titanium dioxide content. is reduced .to a lower valence state in an amount approximating; 10-20% of the slag. This reduced titanium compound. is beneficial in the sulfation of blends in minimizing the amount of metallic iron necessary to eliminate ferric iron in the sulfate solutions prepared therefrom. If the amount of reduced titanium is greatly in excess; of that needed as a substitute for reducing iron, this excess presents substantial problems. It is. the cause of fumes in the sulfation operation and the excess must be eliminated from the solution prior to the recovery of titanium oxide by hydrolytic methods. This is avoided by adjusting the amounts of ilmenite and slag. in, the blend...

The sulfation operation of blends of ilmenite and slag may be carried out in the same type of equipment used heretofore in the sulfation of ilmenite. The reaction is analogous and only slight adjustments need to be made for strength of acid used in the attack of mixtures of the two titaniferous raw materials. In general, the acid should be within the range of about 85-95% H2304, usually between 89% and 93%, and it is obvious that one may use mixtures of 96-100% H2SO4 or oleum and water, steam or weaker acid to obtain the optimum acid strength for the titaniferous material undergoing sulfation.

In addition to the experiments reported above I have conducted further research into the optimum percentage of arizonite type ore and of slag to use in my invention and find that one may be guided by the oxidizing and reducing power of the two titanium bearing raw materials. For a given amount of the arizonite type ore, it is advisable to use in conjunction therewith not more; thanan eou ralent. amount: ofathe. ti -nous slag; The. titanous titanium; of: the.- latteris oxidized. bythe ferric: iron. contentof the 8J1. Zcnite; under such: conditions. The. only: projected. production; of. slag is: at; a. plant. in. Can.- ada; usin the titaniferous ore. from eastern Quebec and giving a product such as that shown in. the experiments outlinedabovel Itis: obvious that, the; composition of. slags: will vary with. the starting; ore; composition, the composition, of coal or coke used. in, the reduction. of the. iron.- content and the. use. of; any fiuxing material, Then; slag; products, should run in excess, of 6.0% T1102. and up t or. r a er than. T102. and will vary as the ore body varies; in composition;- The arizon-ite; ores: are represented by the sands. of India; (Quilon) and of Florida, (Trail Ridge). These; ores contain in excess of about 6.0%.; T1102 and more than half. usually' from 60-80 of; the iron content is. in. the ferric condition, The maximumv benefits of. my process: are: realized when the ferric iron content of the. arizon-ite used. in the mixture is at least stoichiometrically equal. to the titanoustitanium. in the slag. The attack. mass and, the solution made therefrom will, be substantially free of trivalent titanium as the iron actsas an oxidizing agent and. with the slags and arizonite type ores now available this condition prevailswhen the two raw materials are mixed in the proportions of two parts by weight of one to. one part. by weight of the, other-. Optimum advantages of my invention result when one selects an, amount of the arizonite type ore having at least, an amount of ferric iron equivalent tothe trivalent titanium, present in. the slag to be used in admixture therewith (this avoids excessive fuming; conditions during sulfation'). but; not more than two parts by weight of the arizonite type ore: per part by Weight of the slag; Underthese operating conditions the fume nuisance; is substantially lessened if not com.- pletely avoided and the iron content of the.- ill." tanium sulfate solution is kept within the preferred range of from 18 to 35 grams of iron per grams of titanium. oxide. Such. solutions, upon, being, conventionally hydrolyzed provide hydrolysates which yield high-grade TiOz pig.- ments, following calcination: at. temperatures ranging; from, say-, 900-4050," C. They are-readily prepared, as already noted, by dissolving; the sulfatedr ore-slag mixture in water or other suitable aqueous media, such as the dilute. acid. or other forms of licuiors: obtainedin other, stages of the. TiOa-producing system, Obviously, their reduced titanium content can be suitably adjusted, if desired, immediately prior to hydrolysis and in the same manner as is well known in present-day titanium pigment producing operations utilizing ilmenite.

I claim as my invention:

1. A process for preparing a hydrolyzable titanium sulfate solution which comprises reacting a mixture of a titaniferous ore containing in excess of 60% TiOz and an iron content more than half of which is in the ferric condition, and a smelted titaniferous slag having a T102 content of at least 60% and an iron content which is in the ferrous condition only, with strong sulfuric acid until a solid mass containing soluble titanium sulfate is obtained and dissolving said mass in an aqueous solvent.

2. A process for preparing a hydrolyzable titanium sulfate solution which comprises mixing an arizonite ore containing in excess of 60% T102 and having an iron content of which about 60-80% is in the ferric state, with a previously smelted titanium ore having a TiOz content of at least 60% and an iron content which is in the ferrous condition only, reacting the resulting mixture with 85-95% sulfuric acid, and then dissolving the sulfated reaction product in an aqueous solvent.

3. A process for the preparation of a titanium sulfate solution suitable for hydrolysis to precipitate a titanium oxide hydrolysate therefrom which comprises reacting a finely divided mixture of an ilmenite ore having high titanium and high ferric iron content and a titaniferous smelted slag product analyzing 60-80% TiOz and containing iron in the ferrous state only with strong sulfuric acid until a solid mass containing soluble titanium sulfate is obtained and dissolving said mass in an aqueous solvent to obtain the said titanium sulfate solution.

4. A process for the preparation of titanium sulfate solution useful in the production of pigmentary oxide therefrom through hydrolysis and subsequent calcination f the recovered precipitate which comprises reacting with strong H2804 a mixture of a titaniferous ore having a high ferric content and a smelted titaniferous slag product containing 60-80% TiOz, ferrous iron only, and having from -20% of its titanium content in the reduced state, and dissolving the resulting solid titanium sulfate mass in an aqueous solvent to obtain said titanium sulfate solution. I

5. A process for the preparation of titanium sulfate solution suitable for use in the recovery of pigmentary titanium dioxide which comprises grinding a titaniferous ore of the arizonite type in admixture with a substantially equal amount of a titaniferous slag product containing from 60-80% TiOz and an iron content which is in the ferrous state only, reacting the ground product with strong sulfuric acid to produce a solid mass containing soluble titanium sulfate, and dissolving said mass in an aqueous solvent to obtain the final titanium sulfate solution.

6. A process for the preparation of a hydrolyzable titanium sulfate solution useful in the recovery of pigmentary titanium oxide therefrom by well-known hydrolysis methods, which comprises reacting a finely ground mixture of from parts to 65 parts by weight of ilmenite and from 65 parts to 35 parts by weight of titaniferous slag product containing from 60-80% T102 and having a ferrous iron content only, with strong sulfuric acid thereby producing a solid mass containing soluble titanium sulfate and dissolving the latter in an aqueous solvent to obtain the said titanium sulfate solution.

' 7. A process for preparing a hydrolyzable titanium sulfate solution which comprises reacting 85-95% sulfuric acid with a finely divided mixture of an arizonite ore containing from 60-80% of T102 with (-80% of its iron content in the ferric condition, and a titaniferous slag containing from 50-80% of TiOz and an iron content which is in the ferrous state only, continuing said reaction until a solid mass containing soluble titanium sulfate is obtained, and then dissolving said mass in an aqueous solvent to obtain the desired titanium sulfate solution.

8. A method for preparing a hydrolyzable titanium sulfate solution useful in the production of pigmentary titanium dioxide, comprising reacting at an elevated temperature 85-95% sulfuric acid With a finely divided mixture of an arizonite ore and a titaniferous slag product, the TiOz content of both said oreand slag being in the range of from 80% with (30-80% of the iron content or" said ore being in the ferric condition and all of the iron content of said slag being in the ferrous condition, continuing said reaction until a solid soluble titanium sulfate mass is obtained, and then dissolving said mass in an aqueous solvent.

9. A method for preparing a hydrolyzable titanium sulfate solution utilizable in the production of pigmentary titanium dioxide which comprises reacting at an elevated temperature 89-93% sulfuric acid with a finely divided mixture of equivalent amounts of an arizonite ore containing in excess of 60% and up to TiOz with from 60-80% of its iron content being in the ferric condition, and a titaniferous slag product from (50-80% of TiOz with all of its iron content being in the ferrous state, continuing said reaction until a solid mass containing soluble titanium sulfate is obtained, and then dissolving said sulfate in water to obtain the desired titanium sulfate solution.

ROBERT M. McKINNEY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,014,793 Weintraub Jan. 16, 1912 2,413,640 McAdam Dec. 31, 1946 

7. A PROCESS FOR PREPARING A HYDROLYZABLE TITANIUM SULFATE SOLUTION WHICH COMPRISES REACTING 85-95% SULFURIC ACID WITH A FINELY DIVIDED MIXTURE OF AN ARIZONITE ORE CONTAINING FROM 60-80% OF TIO2 WITH 60-80% OF ITS IRON CONTENT IN THE FERRIC CONDITION, AND A TITANIFEROUS SLAG CONTAINING FROM 60-80% OF TIO2 AND AN IRON CONTENT WHICH IS IN THE FERROUS STATE ONLY, CONTINUING SAID REACTION UNTIL A SOLID MASS CONTAINING SOLUBLE TITANIUM SULFATE IS OBTAINED, AND THEN DISSOLVING SAID MASS IN AN AQUEOUS SOLVENT TO OBTAIN THE DESIRED TITANIUM SULFATE SOLUTION. 